Bitmap bmp;

        private void Form1_Load(object sender, EventArgs e)
        {

            bmp = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height);



            Graphics graphics = Graphics.FromImage(bmp);



            int i, j;

            int w = bmp.Width;

            int h = bmp.Height;



            int interval = 5;

//             //每隔5个像素点画设置一个黑颜色点，生成图片。
// 
//             for (i = 0; i < w; i += interval)
//             {
//                 for (j = 0; j < h; j += interval)
//                 {
//                     //使用SetPixel()来设置像素点。
//                     bmp.SetPixel(i, j, Color.Black);
//                 }
            //             }
            bmp.SetPixel(33, 55, Color.Black);
            bmp.SetPixel(5, 3, Color.Black);
            bmp.SetPixel(44, 35, Color.Black);
        }



        private void OnPaint(object sender, PaintEventArgs e)
        {
            Graphics graphics = e.Graphics;

            //显示图片

            graphics.DrawImage(bmp, new Rectangle(0, 0, this.ClientRectangle.Width, this.ClientRectangle.Height));


        }